The proposed research is a project aimed ultimately at elucidating the mechanism of tumor induction by the T antigens of polyoma virus. Since these antigens are available in miniscule amounts from polyoma infected or transformed animal cells, a new source of these proteins will be created - E. coli. The specific goals of the project are: (1) Contruction of recombinant plasmids which, when introduced into the appropriate E. coli host, direct synthesis of each of the three polyoma T antigens; (2) isolation by standard biochemical techniques of purified middle and large T Ag; (3) initial characterization of the purified proteins with respect to their biochemical and biological activities - with special emphasis on their role in the mechanism of polyoma induced neoplastic transformation.